1. Field of the Invention
This invention relates to a method for manufacturing a light emitting device.
2. Background Art
Semiconductor light emitting devices capable of emitting visible light including blue to red light can be widely used in such applications as illumination lamps, displays, and traffic signals. Such light emitting devices with high brightness can find wider application in light sources replacing fluorescent lamps and incandescent bulbs. Furthermore, reduction of operating current facilitates achieving low power consumption.
Here, in a light emitting device which uses a substrate made of e.g. GaAs having a bandgap wavelength of generally 870 nm, visible light emitted from the light emitting device and having emission wavelengths of 700 nm or less is absorbed by the substrate, causing the problem of decreased brightness.
If the substrate is made of e.g. GaP having a bandgap wavelength of generally 550 nm, optical absorption by the substrate can be reduced for visible light having longer wavelengths, which facilitates increasing the brightness. However, the lattice constant of InGaAlP-based semiconductors capable of emitting visible light in the wavelength range from yellow-green to red differs from the lattice constant of GaP by as large as several %, which makes it difficult to directly form an InGaAlP-based light emitting layer with low crystal defect density on a GaP substrate.
JP-A 2005-019424(Kokai) discloses a technique related to a method for manufacturing a light emitting device by wafer bonding. In this technique, a substrate and a light emitting layer section are bonded via a metal layer. Here, a diffusion blocking semiconductor layer is provided to prevent metal diffusion from the metal layer into the light emitting layer, thereby preventing decrease in light emission characteristics.
However, it is difficult to achieve good wafer bonding characteristics while preventing cracking of the substrate in the heat treatment step for substrate lamination.